fix(webapp): return 415 for invalid SSO form content types

[carderne]

Summary

SSO form submissions with an unsupported content type now receive a 415 response instead of failing while parsing the request body.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 9b29027

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[coderabbitai]

Walkthrough

The SSO action now validates the request Content-Type before parsing form data. It accepts URL-encoded and multipart form submissions and returns HTTP 415 for unsupported types. A server-changes entry documents this behavior as a webapp fix.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description is on-topic but missing most required template sections, including issue closure, checklist, testing, changelog, and screenshots.	Add the required template sections: Closes #issue, checklist items, testing steps, changelog summary, and screenshots or N/A.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly matches the change: returning 415 for unsupported SSO form content types.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/tri-11981-return-415-for-unsupported-sso-form-requests

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.